Desulfurization process

ABSTRACT

FIELS OILS OF REDUCED SULFUR CONTENT ARE PREPARED BY SEPARATING A RESIDUE-CONTAINING PRETROLEUM FRACTION INTO A VACUUM GAS OIL AND A VACUUM RESIDUUM, CATALYTICALLY HYDRODESULFURIZING THE VACUUM GAS OIL IN THE PRESENCE OF A CATALYST COMPRISING A HYDROGENATING COMPONENT ON A SUPPORT, THE CATALYST HAVING A SURFACE AREA OF AT LEAST 250 M.2/G., A PORE VOLUME OF AT LEAST 0.6 CC./G/ AND CONTAINING AT LEAST 2 WT. PERCENT SILICA AND COMBINING THE DESULFURIZED VACUUM GAS OIL WITH THE VACUUM RESIDUUM.

United States Patent Ofice 3,804,748 DESULFURIZATION PROCESS Gerald V. Nelson, Nederland, Tex., and Glenn C. Wray, Dyersburg, Tenm, assignors to Texaco Inc., New York,

Ni) Drawing. Filed May 1, 1911, Ser. No. 141,384 Int. Cl. Clllg 23/00, 23/02 US. Cl. 208-211 g 7 Claims ABSTRACT OF THE DISCLOSURE Fuel oils of reduced sulfur content are prepared by separating a residue-containing petroleum fraction into a vacuum gas oil and a vacuum residuum, catalytically hydrodesulfurizing the vacuum gas oil in the presence of a catalyst comprising a hydrogenating component on a support, the catalyst having a surface area of at least 250 m. /g., a pore volume of at least 0.6 cc./g. and containing at least 2 wt. percent silica and combining the desulfurized vacuum gas oil with the vacuum residuum.

This invention is concerned with the removal of sulfur from petroleum hydrocarbon liquids. 'More particularly it is concerned with the production of heavy hy drocarbon fuels of low sulfur content.

The hydrodesulfurization of light petroleum hydrocarbon liquids is well known and has been practiced for many years. Generally, sulfur is present in petroleum in the form of mercaptans, sulfides, di-sulfides and in complex compounds containing ring structures such as thiophenes. In the catalytic desulfurization of lighter petroleum fractions such as gasoline, naphtha and kerosine the sulfur is present to a large extent in the form of easily removable mercaptans requiring less severe desulfurization conditions which make for long catalyst life. The catalyst life is also prolonged in the desulfurization of such light fractions by the low content of polynuclear aromatics present in the charge.

Up until recently attempts have been made to desulfurize heavy residual type petroleum fractions, but for the most part, they have not been too satisfactory. However, with the recent interest in the prevention of air pollution it has become necessary to resort tothe use of industrial fuels of low sulfur content.

The catalytic desulfurization of residual fuels is much more difficult than the desulfurization of lighter fractions. When hydrodesulfurizing residual stocks, contaminants such as metals and carbon residue are deposited on the catalyst. In addition, polynuclear condensed ring aromatic compounds tend to collect on the catalyst and to decompose with the formation of a coke deposit. These deposits cause deactivation of the catalyst and in processes where the product has a maximum sulfur specification this loss in activity is compensated for by increasing the reaction temperature. Unfortunately, when the reaction temperature is increased there is an accompanying increase in the rate of metals deposition and in the rate of deposition of other contaminants on the catalyst and correspondingly the de-activation rate of the catalyst becomes progressively greater. When the reactor temperature has been increased to the maximum limit of the reactor design or when the amount of the conversion to light materials reaches an undesirable level the unit must be shut down to regenerate or replace the catalyst.

We have discovered a novel process for the desulfurization of residual containing fuel oils. According to our invention there is provided a process for the desulfurization of hydrocarbon oils containing at least 1% Conradson carbon and of which at least volume percent boils below about 1000 F. which comprises separating below about 1000 and a heavy fraction boiling above 3,804,748 Patented Apr. 16, 1974 below about 1000 F. and ab eavy fraction boiling above about 1000 F, contacting said light fraction with a desulfurization catalyst under desulfurization conditions and combining the desulfurized light fraction with said heavy fraction.

For a better understanding of the process of our invention, reference is made to the following more detailed description.

The charge is introduced into a fractionator and that portion of the charge boiling up to about 1000 F. is introduced into a desulfurization zone with hydrogen. The reactant stream is subjected to hydrodesulfurization conditions and the eflluent is introduced into a high pressure separator. Hydrogen is removed and may be recycled to the desulfurization zone. The liquid portion of the effluent from the high pressure separator is transferred to a low pressure separator from which gas is withdrawn and sent to gas recovery. The liquid efiluent from the low pressure separator is sent to a fractionator where it is separated into a light fraction such as naphtha, an intermediate fraction such as a light gas oil and a heavy fraction such as a heavy gas oil. The heavy fraction is combined with that portion of the charge having an initial boiling point of about 1000F. to make a fuel oil of reduced sulfur content. Make-up hydrogen may be introduced into the system at any point. Advantageously, to help maintain temperature control, a portion of the make-up or recycle hydrogen may be introduced into the desulfurization reactor and injected into the catalyst bed at intermediate points thereof.

The process of our invention is applicable to a wide variety of charge stocks including whole crude, atmospheric residuum, vacuum residuum, shale oils, tar sand oils, residual fuel oil blends and the like. The charge should contain at least 1% Conradson carbon and should also contain at least 10 vol. percent boiling below about 1000 F. Advantagcously, a portion of light material produced as a by-product of our process may be re cycled to be included as part of the charge. Typically, the. charge stocks contain tar and metals, both of which ordinarily have a detrimental effect on the catalyst life and activity.

The reaction conditions in the hydrodesulfurization zone may be varied, depending on the amount of desulfurization desired and on the charge stock. Temperatures may range from-450900 F., hydrogen partial pressures from 300-8000 p.s.i.g., hydrogen rates from 500-20,000 s.c.f.b. (standard cubic feet per barrel of feed) and space velocities from 01-200 volumes of feed per hour per volume of catalyst. Preferred reaction conditions are temperatures of 500-800 F., hydrogen partial pressures of 500-1500 p.s.i.g., hydrogen rates of from 1000-5000 s.c.f.b. and space velocities of from 05-10.

Hydrogen from any suitable source such as electrolytic hydrogen, hydrogen obtained from the partial combustion of a hydrocarbonaceous material followed by shift conversion and purification or catalytic reformer by-product hydrogen and the like may be used. The hydrogen should have a purity of at least 50 volume percent, satisfactory results having been obtained using hydrogen having a purity of between and volume percent.

The catalysts used in the process of our invention comprise a Group 8 metal compound such as the oxide or sulfide of cobalt, iron or nickel or mixtures thereof advantageously used in conjunction with a Group 6 metal compound such as the oxide or sulfide of molybdenum or tungsten. Ordinarily, the catalyst is charged to the reactor in oxide form although it can be expected that some reduction and some sulfidation takes place during the course of the process so that after being on stream for some time the catalyst is probably a mixture of the metal, the metal sulfide and perhaps the oxide." The Group 8 metal compound may be present in an amount varying from 1 to 20 percent by weight of the catalyst composite. The Group 6 metal compound may be present in an amount ranging from about to 40 percent of the total catalyst composite. Ordinarily, the hydrogenating components are supported on a refractory inorganic oxide such as alumina, zirconia, silica or magnesia or mixtures thereof. Particularly suitable catalysts comprise nickel and tungsten, cobalt and molybdenum or nickel anr molybdenum on a refractory support. To obtain particularly long life, the catalyst should have a surface area of at least 250 sq. meters per gram, preferably at least 300 sq. meters per gram and a pore volume of at least 0.6 cc. per gram. The catalyst should also contain at least 2% by wt. silica, for example, 2-15% and preferably 2-8 wt. percent.

The reactant flow through the catalytic zone may be I downflow through a fixed catalyst bed, 'but it is also possible to pass the reactants upwardly or counter-currently through the catalyst bed. It should also be realized that the catalyst may be used in the form of a slurry or as a fluidized bed.

The following example is presented for illustrative purposes only.

EXAMPLE In this example, the catalyst has the following composition and characteristics:

TABLE 1 Surface area, mF/gm. 312 Pore volume, cc./gm. 0.66 Bulk density, lbs/ft. 44.0 Composition, wt. percent:

Co 1 2.1 Mo 1 11.0 ,SiO 3.3 A1 0 Remainder 1 Present in oxide form.

The charge stock is an atmospheric residuum obtained from Lago Medio crude containing 7.4 wt. percent Conradson carbon residue and 1.85 wt. percent sulfur with 65 vol. percent boiling below 1050 F. The sulfur content of the fraction boiling up to 1050 F. is 1.44 wt. percent and of the fraction boiling above 1050 F. is 2.55 wt. percent.

Reaction conditions for desulfurization of the fraction boiling up to 1050 F. are tabulated below as are the sulfur contents of the desulfurized vacuum gas oil and the blend produced by recombining it with the vacuum residuum.

TABLE 2 Catalyst bed temp., F 700 Hydrogen partial pressure, p.s.i.g 750 Reactor feed gas rate, s.c.f.b 2000 Feed gas purity, vol. percent H Space velocity, v./v./hr. 1.0 Sulfur, wt. percent:

IBPl050 F 0.13

Blend 0.95

than4'000 hours'of operation.

Obviously, various modifications of the invention as hcreinbefore set forth may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A process for the production of a residue-containing petroleum oil of reduced sulfur content which consists essentially of separating by distillation under sub-atmospheric pressure a petroleum oil feed comprising an atmospheric residuum containing at least 1% Conradson carbon residue and of which feed at least 10% by volume boils below about 1000 F. into a vacuum gas oil having an end boiling point of about 1000 F. and a vacuum residuum having an initial boiling point of about 1000 F., passing said vacuum gas oil through a fixed bed of desulfurization catalyst comprising a Group VI metal or compound thereof and a Group VIII metal or compound thereof and having a surface area of at least 250 m. g. and a pore volume of at least 0.6 cc./g. and containing at least 2% by weight silica at a temperature between about 450 and 900 F. and a hydrogen partial pressure between about 300 and 3000 p.s.i.g., combining at least a portion of the desulfurized vacuum gas oil with at least a portion of undesulfurized vacuum residuum and controlling the temperature in the desulfurization Zone by introducing hydrogen into the catalyst bed at an intermediate point thereof.

2. The process of claim 1 in which the desulfurization catalyst comprises nickel and tungsten.

3. The process of claim 1 in which the desulfurization catalyst comprises nickel and molybdenum.

4. The process of claim 1 in which the desulfurization catalyst comprises cobalt and molybdenum.

5. The process of claim 1 in which the catalyst has a surface area of at least 300 m. g. and a pore volume of 0.6-0.8 cc./g.

6. The process of claim 5 in which the catalyst contains 2-15 weight percent silica.

7. The process of claim 1 in which the reactants are passed downwardly thorugh a fixed bed of catalyst.

References Cited UNITED STATES PATENTS 3,617,525 4/1969 Moritz et a1. 208-2l1 3,617,526 11/1971 Coons, Jr., et al 208-211 3,471,399 10/1969 OHara 208-216 3,393,148 7/1968 Bertolacini, et al. 208-216 X 2,878,179 3/1959 Henning 208-210 X 3,306,845 2/ 1967 Poll 208-210 X 2,973,313 2/1961 Pevere et al. 208-211 X DELBERT E. GANTZ, Primary Examiner I. M. NELSON, Assistant Examiner US. Cl. X.R.

" UNE'FED smwzs LATENT @FFEQE @ERTEFEQATE QQFfiEQEfiW Patent No. 3,80%, h8 I Dawa A il 16, 197

Inventor) Gerald V. Nelson Glenn C. may

It is certified fihat ewe? appears in the above-identified patent and that said Letters Patent are ne'm'sy cot-mated as shown below:

9-- COLUMN '1, last line, shaul-iz f said heavy hydrocarbon 013. into a light fraction boiling CLAIM 7, line 2, "choxwmgi: should read --through-- si ned and sealed t'hi 10th day 01" September 1971+.

(SEAL) Attest:

McCoy M. GIBSUN', JR. c. MARSHALL DANN Attesting Officer Commissioner" of Patents 

